The fix to getting this function to work again is pretty simple as it's a simple language issue. Unfortunately, the command for now only seems to be working with the English language and not any other.
Basically you need to change your voice search language to English because it's quite possible that it's set on a different language, possibly yours. Now you don't need to change the whole interface language but actually just the voice search one, so you can keep your default system language.
- Head into Settings
- Now look for "Language & input" and go there
- Look for and go to where it says "Voice search" - this one should be somewhere at the bottom
- Now select "Language"
- Change the language to English (US)